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50KHz Glideslope?



 
 
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  #11  
Old April 2nd 09, 12:13 AM posted to rec.aviation.ifr
Ron Rosenfeld
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Posts: 264
Default 50KHz Glideslope?

On Tue, 03 Mar 2009 21:47:22 -0800, VOR-DME wrote:

Who knows something about 50KHz spacing for glideslope receptors?
Traditionally we have 40 GS frequencies, with 150KHz spacing from
329.15MHz to 335 MHz. But I see European ILS's requiring "50KHz
Glideslope spacing". Anyone know what receptors do this? Or why we would
want to do this? 8.33 spacing for VHF coms is easy to understand, but
are 40 ILS frequencies in a given reception area really insufficient?


Hmmm.

How are these new frequencies being implemented? Do you have some
documentation?

Currently, each ILS frequency is channeled to a particular GS frequency.

Given 50kHz spacing, and given that the ILS frequencies are 108.10 to
111.95 (and given that if the Freq*10 is even, it is a VOR frequency),
there are only 40 available ILS channels in that frequency range:

e.g. 108.10
108.15
108.30
108.35
...

The 150kHz spacing from 329.15-335 also results in 40 GS frequencies.

So unless there is some change in the ILS specs, it seems odd that there
should be a change in the GS specs.

Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)
  #15  
Old April 2nd 09, 08:10 PM posted to rec.aviation.ifr
VOR-DME
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Posts: 54
Default 50KHz Glideslope?

I agree with everything you say.
That's why I asked the question, because I am faced with several approach
plates which specify "Requires 50KHz Glideslope". I cannot find anything
about this in any documentation, so I have no idea what this note means.

I think what I'll do is fly a vor or loc approach at one of these and see if
the GS comes in on the KX155A. If so, I'll just guess that note is of no
importance, and relates to something very old and forgotten.



In article ,
says...


Hmmm.

How are these new frequencies being implemented? Do you have some
documentation?

Currently, each ILS frequency is channeled to a particular GS frequency.

Given 50kHz spacing, and given that the ILS frequencies are 108.10 to
111.95 (and given that if the Freq*10 is even, it is a VOR frequency),
there are only 40 available ILS channels in that frequency range:

e.g. 108.10
108.15
108.30
108.35
...

The 150kHz spacing from 329.15-335 also results in 40 GS frequencies.

So unless there is some change in the ILS specs, it seems odd that there
should be a change in the GS specs.

Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)


  #16  
Old April 9th 09, 02:53 AM posted to rec.aviation.ifr
Ron Rosenfeld
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Posts: 264
Default 50KHz Glideslope?

On Thu, 02 Apr 2009 11:10:38 -0800, VOR-DME wrote:

I agree with everything you say.
That's why I asked the question, because I am faced with several approach
plates which specify "Requires 50KHz Glideslope". I cannot find anything
about this in any documentation, so I have no idea what this note means.

I think what I'll do is fly a vor or loc approach at one of these and see if
the GS comes in on the KX155A. If so, I'll just guess that note is of no
importance, and relates to something very old and forgotten.


I have finally been able to find the chart to which I believe you are
referring (ILS/DME TNO RWY 25R) and I believe you have misquoted the
requirement, and mis-understood the meaning.

The chart that I am examining on line does NOT read "Requires 50KHz
Glideslope"

Rather, the box I see reads:

"GP usable only by ACFT equipped with ILS at 50 kHz"

ou, en française:

"GP utilisable uniquement par ACFT équipé ILS à 50 kHz"

This means that the spacing on the **ILS** receiver needs to be 50 kHz.
Makes sense since the LOC frequency is 110.15.

Your KX155A should have no problem tuning this approach, and channeling the
correct GP frequency, so long as your KX155A can tune 110.15 and has a GP
receiver.

Having read that, it seems to be a strange note because, if your ILS
receiver could not tune in 50 kHz increments, you wouldn't be able to use
the LOC or LLZ approach either! In the US, I would ask our local Flight
Standards District Office for clarification if I saw a note like that. But
I would not be concerned about flying it with a KX155.
Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)
 




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